Yes, this is completely normal, because there are few actors in Bitrefill's market, volume is probably not too high, and bitcoin payments are actually new. Normal paths of evolution of this situation are: 1. If results are too good, other actors will start competing, lowering general fees due to competition. 2. If results are bad, the market will shrink, and probably a different business model will emerge.
3. and this is the most likely in long term: Merchants will try to cut the middleman, accepting BTC directly. That is what has happened in my country with banks, now payment processors (usually associated with stores like Walmart, Mercadolibre, etc) literally have become banks (setting up checking accounts in 5 minutes), driving account monthly fees to literally zero, taking over the checking accounts market. The same to some extent has happened to the credit market, where regular banks have also lost share, but with much fiery legal battle.